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Queso Bandit 04-17-2009 11:58 AM

glass tiles over kerdi (thinset question)
Hi- I've looked all over online and there seem to be many different thinset opinions...

I have 2"x1" glass tiles (mesh backing) for a shower stall that I want to install over kerdi.

Schluter recommends unmodified thinset, glass tile (supposedly) requires modified. I called Schluter and the rep said to more or less go with the glass tile mfg's recommendation (if they can even be used on a bonded waterproof membrane) but cure time for modified will be 14 to 60! days.

I understand the curing differences of the mod/ unmod, but wouldn't tiles this small get enough air through the spacing to allow the modified thinset to dry?

Has anyone installed glass tiles with any success?

I don't care about warranties/ etc. I just don't want the tile to fall off after all that work!
Unfortunately glass and kerdi are already ordered, so I'm stuck in this predicament.

ccarlisle 04-17-2009 12:38 PM

I'd go with unmodified over the Kerdi and under the tile because of the way unmodified dries. Modifed evaporates and while there may be enough room to evaporate through, I don't dispute the 14-60 day drying time.

Plus glass tile mfgs don't always outline every case. They may not have thought about Kerdi. So go with Kerdi and use unmodified.

I did a shower last year with glass tiles and it was fine. White...

Queso Bandit 04-17-2009 03:01 PM

Thanks for the reply.
I take it you had no tile bonding issues w/ an unmodified thinset?
Do you recommend a certain brand/type?

ccarlisle 04-17-2009 03:29 PM

No issues really, although the tiles were so thin, about 1/8" that on the floors they had isues.

Mapei products have a plant hereby here so everyone has theirs.

R&D Tile 04-18-2009 07:45 PM

I would never use unmodified with glass, use whatever the glass manufacturer wants you to use with their product, kerdi or no kerdi.

ccarlisle 04-19-2009 06:46 AM

R&D, OK, but your reasoning is based on what exactly...? what knowledge can the manufacturers of an inert, non-absorbent piece of glass tile impart to us that upsets the commonly-accepted theories of the curing mechanisms of cement?

What proportion of glass manufacture is represented by glass tile anyway? or is this something they have spent years and years and billions of $ researching? How familiar are glass tile manufactures with Kerdi? Not sure the answer is obvious.:no:

I might accept your idea of using modified if you suggested that the thickness of the glass tile, being something like 2mm in some cases, makes adhesion around the edges of each tile super-critical and therefore a quick-drying, high-adhesion product is needed. But I'd come back with the question as to how do you expect the liquid solvents to evaporate sandwiched between Kerdi and glass? Isn't this a larger question that the edges situation?

And doesn't the fact of 14-60 day curing times say anything to you? To me it says the product is not working as it should...not the tile - but the modified.

On the other hand as I have already pointed out, unmodified mortars do not need excess drying conditions and cure internally by hydration as you know. So the curing mechanism is quite different...besides this is the method suggested by Schluter - whose membrane is the base upon which the glass must adhere. Same thinking as why you use unmodified mortar under tile and over Ditra...two impermeable surfaces there too...

Are you countering that method too? If so, why wouldn't, say, porcelain tile manufacturers also push for modified? Do they?:whistling2:

I, for one, would be interested in your thinking here. And also on the glass tile manufacturers thinking too...

Look - I may be completely wrong in my thinking here; I value your opinion R&D and hope you will correct me!:wink:

Gary in WA 04-19-2009 07:32 PM

Just from what I've read. CBP-MegaLite (White), TEC- Superflex (White), Mapei- GraniRapid (White). Tape them up till they set enough. No notched trowel if translucent. Please correct me if I'm wrong. Be safe, GBR

R&D Tile 04-19-2009 07:55 PM

Glass mosaics will cure fine with modified over Kerdi, as it also does with any waterproofing membrane, all the others you can use modified and it works too.

Ditra has those waffles, which makes curing harder for modified thinsets, I use Versabond with porcelain and all my tile installations over Ditra and Kerdi and have never had an issue, hard to find an unmodified thinset that's any good, only two I would even think of using would be Kerabond or Ditraset, both of which are hard to find by me, so for now I'll use what I know works.

If I have to install glass and it needs to be over a waterproof substrate and Kerdi will be an issue, I'll use other products, such as Hydroban or Wedi which have no issues with using modified thinsets over them.

Glass is still a crap shoot, larger the glass more issues you'll probably end up dealing with.

If I can't find what the manufacturer of the glass wants and usually it's a choice among a few highly modified thinsets, I use the laticrete grout and additive system that makes a colored thinset, then use the same grout with their grout additive to grout them, never had an issue yet.

R&D Tile 04-19-2009 07:59 PM


No notched trowel if translucent.
You use a notched trowel, then flatten the thinset before setting the glass.

Queso Bandit 06-11-2009 10:51 PM

FYI for those with the same issue...
I ended up using versabond. Set up fine and no problems so far. :thumbup:

diy108 06-16-2009 01:42 PM

Schluter Kerdi mat and glass tile installation
Wondered how you made out with the conundrum of glass tile and unmodified mortar over kerdi mat. We have got the Maipei Keribond?keralastic and wondered if this was a suitable adhesive.

diy108 06-16-2009 02:24 PM

Lots of info
Just got off the line with our Schluter Rep, and apparently a modified mortar with deeper bedding so that the mortar reaches around the edge of the glass tile like fingers to grab the tile and a longer than normal setting time is required. Also the mesh backing should be bonded to the tile with waterproof glue (glass not recommended for flooring). Modified mortar should be suitable for heavy water exposure ie: fountains

JohnFRWhipple 05-15-2012 03:08 PM

Schluter Systems does not print any recommendations for glass tile installations over Kerdi. They go as far as printing in their FAQ guidelines to call on a case by case basis. Sean Gerolimatos, technical services manager for Schluter Systems was interviewed by JLC in this article Some great information here about "ghosting" with glass tile.

The TCNA in every shower detail requires that the glass manufacture to specify the setting material. This is because I believe the different manufacturing processes used in creating these glass tiles and the different ways of producing sheets.

Most glass manufactures that I have contacted require the use of a modified thin-set. If you have Kerdi on the walls already then a good option is to use only setting materials made by Ardex - Ardex is another German company that has designed their products to work with Kerdi and will provide a warranty if you ask first. You will ofcourse need to use Ardex's grout as well.

Glass tile needs flexability and a dryset mortar preforms very poorly here. A S2 mortar like Grani Rapid from Mapei is outstanding and is a highly modified thin-set.

If you prefer working with a sheet membrane then I suggest using Noble Companies Noble Seal TS or Dal Tile's Dal Seal TS - both of these membranes offer you up the ability of using modifed thin-sets. Likewise Mapei's Aqua Defence, Custom's Red Guard or Laticrete's Hydro Ban the same options of any modified thinset with their liquid membranes.

The new TCNA 2012 Specification guide will be out soon and has a new section of glass tile. Until such time make sure you contact the glass tile manufacture for proper installation directions and ensure that the tile is all installed the same way up if directional arrows are included.

Good Luck.

John Whipple
By Any Design Ltd.
North Vancouver.

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